The present invention relates to agricultural implements; and more particularly, to large agricultural implements adapted to be pulled by a tractor with the frame of the implement extending transverse of the direction of travel of the tractor in field use, and extending parallel to the direction of travel for road transport. An implement of this type was disclosed in my co-pending application Ser. No. 424,890 for AGRICULTURAL IMPLEMENT CONVERTIBLE BETWEEN USE AND TRANSPORT POSITIONS, filed Sept. 27, 1982 now U.S. Pat. No. 4,506,904 issued Mar. 26, 1985.
The implement disclosed in the above-identified application was particularly adapted for planting, although the frame (or "carrier" as it is sometimes referred to) is adaptable for a wide range of implements, such as tillage implements, anhydrous ammonia or fertilizer applicators, as well as other uses. The carrier frame of that implement was non-folding, such as the rear-folding frame disclosed in my U.S. Pat. No. 4,117,893, although that carrier frame is articulated in the sense that individual sections may pivot relative to one another about axes parallel to the direction of travel of the tractor during use so as to conform better to variations in the contour of the field. The carrier frame of that implement is attached to the tractor by a hitch assembly which includes a main draft member pivoted at its rear and adaptable to be moved between a use position in which it extends parallel to the direction of travel of the implement and is generally centered on the implement, and a transport position in which it is pivoted to the side and extends generally parallel to the direction of elongation of the frame. A secondary draft member is pivotally connected at its rear end to the main frame at a location between the center and one end of the frame, and its forward end is latched to the forward end of the primary draft member in the use position. In other words, in the use position, the primary and secondary draft members formed a triangle with the carrier frame for rigidity.
When the implement was converted to the road travel configuration, the secondary or inclined draft member acted as a control link, and its forward end was unlatched from the forward end of the primary draft member; and the control link was rotated to the side of the carrier frame to become the primary draft member in road transport. As the secondary draft member is rotated to the road travel position, a steering mechanism is actuated to rotate the support wheels 90.degree. so that they are also used as the support wheels during road transport; and the support wheels are also steerable by the tractor in the road transport position. This implement has proven to be a significant improvement over prior implements, and it has particular advantages as a frame for a large agricultural planter, capable, for example, of transporting as many as 24 individual planter row units spaced laterally relative to one another at 30 inch intervals.
The present invention provides for certain improvements in an implement frame of the type just described, particularly in the hitch mechanism and in the steering mechanism.
By way of convention, the "front" of the implement or frame indicates the direction in which the frame is pulled during field use; and as is conventional, the left and right sides of the frame correspond to the left and right sides of a person looking in the direction of travel during use.